ASP.NET Programming with C# and SQL Server - Chapter 3

ASP.NET Programming with C# and SQL Server - Chapter 3 Summary

• Chapter 3 covers using functions, methods, and control structures in ASP.NET programming with C# and SQL Server.
• Objectives include learning to use functions to organize C# code, working with the Request object, using if, if...else, and switch statements for decision-making, and using while, do...while, and for statements for repeated code execution.
• Functions group programming statements into logical units. They are procedures used to organize related C# statements.
• Code declaration blocks contain ASP.NET functions and global variables. The <script> element defines a code declaration block, specifying the scripting language (e.g., C#) and execution environment (e.g., server-side).

Defining Functions

• Define a function before using it.
• Function definition contains the lines of code that make up a function.
• Syntax: returnDataType functionName(parameters) { statements; }.
• Return data type indicates the output type. void means the function doesn't return a value.
• Parameters are variables used within a function. They are placed inside the parentheses of the function definition, with each parameter's data type declared.

Calling Functions

• Function definition alone does not execute the function.
• Calling a function invokes or executes it.
• Function call is the code that invokes a function.
• Syntax: functionName(argument1, argument2, ...);.
• Arguments are the values passed as input to a function in the function call. Arguments are also called actual parameters. They are assigned to the function parameters.

Returning Values

• A function may return a value.
• Returned value can be assigned to a variable.
• Syntax: variable = functionName(parameters);
• A return statement in a function sends a value back to the code that called it.
• Syntax: return variable;

Understanding Variable Scope

• Scope defines where a variable can be accessed. It is determined by where the variable is declared.
  • Global variables are declared outside of functions within a code declaration block and are available throughout the entire page.
  • Local variables are declared inside functions or code blocks and are only available within that function or code block.

Working with the Request Object

• The Request object is a built-in ASP.NET object representing a client's URL request.
• The Request object uses collections to store object properties
• Syntax: to access an object collection: object.collection("property")
• Form collection contains variables representing form elements from a web page.
• Example: Request.Form["name"]
• There are many request collections (e.g., cookies, query string, server variables, clients certificates). Each contains specific data.

Making Decision

• Decision-making (or flow control) determines the order in which statements execute in a program.
• The if statement is the most common decision-making statement.
• The if statement executes statements when a conditional expression is true

if...else Statements

• An if...else statement executes one set of statements when a conditional expression is true and another when it's false.
• One, and only one, set of statements will be executed.

Nested if and if...else Statements

• A nested decision-making structure has one decision-making structure contained within another.

switch Statements

• A switch statement executes a specific set of statements depending on the value of an expression.
• A matching case label activates the corresponding block of statements.
• Provides an alternative to a series of nested if...else statements when multiple conditional checks are needed.

Repeating Code (Loop Statements)

• Loop statements repeatedly execute a block of statements.
• Types include while, do...while, and for.
  • while: repeats statements as long as a conditional expression evaluates to true.
  • do...while: executes statements once and then repeats as long as the conditional expression is true.
  • for: used for repeating a block of code, often with a counter variable that increments or decrements with each iteration.

Using continue Statements

• A continue statement skips the remaining statements within the current loop iteration, but allows the loop to proceed with a new iteration.

Summary

• Key components like <script> blocks, functions, scopes (global and local), the Request object, decisions (if/else, switch), and loops (while, do...while, for) are used to build dynamic web applications in ASP.NET C#.